Delivery system and method for interstitial radiation therapy using seed strands with custom end spacing

ABSTRACT

A delivery system and method for interstitial radiation therapy comprising a substantially axially stiff and longitudinally flexible elongated strand made of material, which is bio-absorbable in living tissue and a plurality of radioactive seeds dispersed in a predetermined array within the strand. The delivery system and method further customize the strand based on a prescription. The strands can have custom end spacings, which allow the optimal placing of seeds within the treatment tissue by implanting a plurality of strands to the same depth. A plurality of these strands can be implanted at the same time by the use of a guiding device.

CLAIM OF PRIORITY

The application is a continuation of U.S. patent application Ser. No.10/619,928, filed Jul. 15, 2003 (now allowed), which claims priorityunder 35 U.S.C. 119(e) to U.S. Patent Provisional Application60/469,940, filed May 13, 2003, both which are incorporated herein byreference.

CROSS-REFERENCE TO RELATED APPLICATIONS

The following applications are cross-referenced and incorporated hereinin their entirety:

U.S. Patent Application No. 60/360,237, entitled “System forManufacturing Interstitial Radiation Therapy Seed Strands”, byTerwilliger et al., filed Feb. 26, 2002.

U.S. Patent Application No. 60/360,272 entitled “Delivery System andMethod for Interstitial Radiation Therapy Using Strands Constructed withExtruded Strand Housing”, by Terwilliger et al., filed Feb. 26, 2002.

U.S. patent application Ser. No. 10/162,548 entitled “Delivery Systemand Method for Interstitial Radiation Therapy Using Strands Constructedwith Extruded Strand Housing”, by Terwilliger et al., filed Jun. 4,2002.

U.S. patent application Ser. No. 10/162,546 entitled, “System forManufacturing Interstitial Radiation Therapy Seed Strands” byTerwilliger et al., filed Jun. 4, 2002.

U.S. patent application Ser. No. 10/162,006 entitled, Delivery Systemand Method for Interstitial Radiation Therapy Using Strands Constructedwith Extruded Strand Housings”, by Terwilliger et al., filed Jun. 4,2002.

U.S. patent application Ser. No. 10/397,940 entitled, “Delivery Systemand Method for Interstitial Radiation Therapy” by Terwilliger et al.,filed Mar. 26, 2003.

U.S. patent application Ser. No. 10/035,083 entitled, “Delivery Systemand Method for Interstitial Radiation Therapy” by Terwilliger et al.,filed Dec. 28, 2001.

U.S. Patent Application No. 60/336,329 entitled, “Delivery System forInterstitial Radiation Therapy” by Terwilliger et al., filed Nov. 2,2001.

FIELD OF THE INVENTION

The present invention relates to systems and methods for delivering aplurality of radioactive sources to a treatment site.

BACKGROUND

In interstitial radiation therapy, one method for treating tumors is topermanently place small, radioactive seeds into the tumor site. Thismethod is currently accomplished by one of the following two procedures:(a) loose seeds are implanted in the target tissue, and/or (b) seeds arecontained within a woven or braided absorbable carrier such as braidedsuture material and implanted in the target tissue. The loose seeds,however, are dependent on the tissue itself to hold each individual seedin place during treatment, and the woven or braided sutures do notassist in the placement of the seeds relative to the target tissue.

There have been many developments in brachytherapy (i.e., therapyrelating to treating malignant tumors for handling such radioactiveseeds). In one technique, hollow metal needles are inserted into thetumor and the seeds are thereafter inserted into the needles, while theneedles are being retracted to deposit the seeds in the tumor. Suchdevices are shown in U.S. Pat. No. 4,402,308, which is incorporatedherein by reference. The most commonly used instruments are the Henschkeand Mick devices. The use of such devices has distinct disadvantages.The overall length of such devices is over 20 inches and such deviceshave significant weight making them difficult to manipulate.

Another disadvantage of the above technique is that the seeds aredeposited in a track made by the needle. When the needle is withdrawn,there is a tendency for the seeds to migrate in that track resulting ina poor distribution of the seeds. Because the energy levels are low,distribution between centers of adjacent seeds should be on the order ofabout 1 cm for certain treatments. Poor distribution of seeds can resultin undesirable concentrations of seeds resulting in either anover-dosage or under-dosage of radiation. Further, over time, the seedstend to migrate along the needle track, away from the tumor, andaccordingly patients commonly must repeat the procedure within a couplemonths to have seeds re-implanted near the tumor.

Further complicating the procedure is the fact that the seeds are small,because they need to fit in small bore needles to prevent excessivetissue damage. Due to their small size and high seed surface dose, theseeds are difficult to handle and to label, and can easily be lost. Inaddition, the technique of implantation of individual seeds is timeconsuming.

One preferred method of introducing seeds into the tumor site is using apre-manufactured elongated assembly or implant that contains seedsspaced at 1 cm increments. This assembly is capable of being loaded intoan introducer needle just prior to the procedure. What is desired inusing an elongated assembly of seeds and spacers is the ability toinsert such an assembly into a tumor site to provide controlled andprecise placement of the radioactive seeds.

While assemblies with bio-absorbable materials and spaced radioactiveseeds are known for use as interstitial implants, such assemblies arenot entirely satisfactory. In one instance, the elongated implant ismade using a bio-absorbable material consisting of an EthiconVicryl.RTM. This material is commonly known as PGA. Radioactive seedsand teflon spacers are inserted into the material. The carrier is heatedcausing contraction of the carrier material and resulting in a rigidcolumn of seeds and spacers. This technique was reported in“Ultrasonically Guided Transperineal Seed Implantation of the Prostate:Modification of the Technique and Qualitative Assessment of Implants” byVan't Riet, et al., International Journal of Radiation Oncology, Biologyand Physics, Vol. 24, No. 3, pp. 555-558, 1992 which is incorporatedherein by reference. Such rigid implants have many drawbacks, includingnot having the ability to flex with the tissue over the time that thebio-absorbable material dissolves.

As the tissue or glands shrink back to pre-operative size, and thus asthe tissue recedes, a rigid elongated implant does not move with thetissue, but remains stationary relative to the patient. The finallocation relative to the tumor is thus not maintained and the dosage ofthe radioactive seeds does not meet the preoperative therapy plan.

Another system for providing an elongated implant having radioactiveseeds disposed therein is disclosed in U.S. Pat. No. 4,697,575, which isincorporated herein by reference. In this reference, a plurality ofencapsulated radioactive seeds are positioned in a predetermined array.The seeds are encapsulated in individual capsules, with each capsulehaving a projection on one capsule end and a complementary recess on theremaining capsule end. A projection in one capsule is engageable with arecess in an adjacent capsule such that the desired number of seeds canbe plugged together to form a column of rigid, bio-absorbable andelongated material. This implant is not entirely satisfactory inasmuchas it is time consuming and inefficient to carry out the manipulativesteps of assembling such a strand of elongated material. Further, theimplant is quite rigid as it is inserted into a patient without the useof an introduction needle, as the implant itself acts as a rigid needlethat is undesirably left in place.

In another embodiment disclosed in the above patent, a rigid implantcontaining radioactive segments, with break points, is inserted into thetumor. The implant is made of a bio-absorbable polymer that is rigidenough to be driven into the tumor without deflection and without theuse of a separate hollow needle. When the proper depth is reached withthe rigid polymer needle, the remaining, uninserted portion of theneedle is broken off. This embodiment has the disadvantage of the aboveembodiment, in that being too rigid, the implant does not follow thetumor as it shrinks back to its normal size.

In U.S. Pat. No. 6,163,947, Coniglione, issued Dec. 26, 2000, andincorporated herein by reference, a string of hollow seeds described inU.S. Pat. No. 5,713,828, issued Feb. 3, 1998, also incorporated hereinby reference, are strung onto a thin strand of suture material to forman array of seeds. This string of seeds is delivered into the tumor siteplaced within a hollow needle. Since the hollow lumen of the seeds aresubstantially smaller in diameter in relation to the outside diameter ofthe seed body, the string of suture material must be substantiallysmaller in diameter than the seeds themselves. The resulting diameter ofthe suture makes the suture axially weak and the suture can fold upbetween the seeds within the needle lumen as pressure is applied on theproximal end of the strand within the needle. Thus the difference indiameter between the seed and the thin suture material makes theassembly susceptible to collapse from axial force applied on theproximal end, resulting in jamming of the assembly within the needlelumen and/or the assembly not maintaining the proper desired spacingbetween radioactive seeds as the assembly is expelled into the treatmentsite.

One relevant reference discloses modification of the needle structure toinclude a reloadable cartridge. In such reference, the needle isinserted and as a cartridge of seeds is emptied, the plunger of thedevice is withdrawn and a new cartridge containing radioactive seeds isloaded into the syringe (Moore, U.S. Pat. No. 4,086,914, issued May 2,1978). Another reference offers a device for implanting individual seedsin a planar dispensing device with multiple needles to ensure accurateplacement of the seeds relative to one another and the treatment site(Kirsch, U.S. Pat. No. 4,167,179, issued Sep. 11, 1979). Anotherreference disclosed a shielding devices for bead strands which preventsradiation exposure for health care personnel performing treatment withthe radioactive seeds (Windarski, U.S. Pat. No. 4,509,506 issued Apr. 9,1985). All of the above references are incorporated herein by reference.

In another technique for treating tumors disclosed in U.S. Pat. No.5,460,592, and incorporated herein by reference, seeds are held in awoven or braided bio-absorbable carrier such as a braided suture. Thecarrier with the seeds laced therein is then secured in place to form asuitable implant. This braided assembly exhibits many drawbacks, such aswhen the braided assembly is placed into the tumor. The needle thatcarries the braided assembly must be blocked at the distal end toprevent body fluids from entering the lumen. If body fluid reaches thebraided assembly while the assembly is still in the lumen of the needle,the braided assembly can swell and jam in the lumen. Because theassembly is made of a braided tubular material, it is difficult to pushthe assembly out of the needle. As the needle is withdrawn from thetumor, pressure on the proximal end of the braided assembly causes thebraid to expand and jam inside the lumen of the needle. Finally, if thebraided strand is successfully expelled from the needle, the relativespacing of the seeds may not be maintained, if the braided material hascollapsed.

Other references that address such implants and materials include thefollowing, all of which are incorporated herein by reference.

1. U.S. Pat. No. 1,578,945, issued January 1923 to Withers;

2. U.S. Pat. No. 2,067,589, issued January 1937 to Antrim;

3. U.S. Pat. No. 3,351,049, issued November 1967 to Lawrence;

4. Medi-Physics brochure entitled AI-125 Seeds.RTM. In Carrier,@ ModelNo. 6720;

5. Medi-Physics brochure entitled AI-125 Seed.RTM. Source Model 6711;”and

6. Martinez et al., Int. J. Radiation Oncology Biol. Phys., Vol. 5, No.3, Mar. 1979, pp. 411-413.

SUMMARY OF SOME ASPECTS OF THE INVENTION

Accordingly, the present invention cures and addresses the disadvantagesexhibited in the prior art devices and implants. What is desired is toprovide a bio-absorbable carrier material having seeds disposed withinthe material, with the seeds being accurately spaced a predetermineddistance from one another, and with the seeds repeatably maintainingthat spacing, even after being introduced into the body.

It is also desired that an elongated member with seeds be sufficientlyrigid axially to allow expulsion of the member while maintaining thespacing between seeds, and that the member be flexible and pliableenough to move with the tissue as the tissue shrinks back topre-operative size.

In a further aspect, an embodiment of the invention has an end spacingconfigured to match the relative distance the needle needs to beretracted after the initial insertion in order to position the needlerelative to a site, eliminating retraction prior to see placement, andallowing all needles to be inserted to the same depth in the patient,thus reducing implant time.

It is further desired to shorten the time required for the preparationand implantation of a plurality of these elongated members.

Accordingly, some of the objectives of the present invention includeproviding an elongated member with seeds dispersed throughout, whichobviates the aforementioned disadvantages and allows placement of theseeds in accurate positions to provide the desired interstitialradiation dose to the location derived from a preoperative dosimeterplan.

A further object of the present invention is to provide a deliverysystem for interstitial radiation therapy, which is faster and easier touse than prior art systems.

Another object of the present invention is a delivery system that causesa minimum of trauma to tissue.

A related object is to have the ability to implant a plurality of thesedelivery systems at the same time.

Yet, another object of the present invention is a delivery system thatallows for control of the radiation dosage given the tissue. Stillfurther objects of the present invention are a delivery system that canbe used and placed with precision, and that maintains the position ofthe implant after the implantation, until the bio-compatible materialdissolves and the seeds have become inert. In another aspect, thebio-compatible material is selected to absorb about when the half-lifeof the radioactive seeds is reached.

A further aspect is to have the implant be echogenic.

In accordance with an embodiment of the invention, the delivery systemcomprises a substantially axially stiff and longitudinally flexibleelongated member that is bio-absorbable in living tissue. The member hasa length that greatly exceeds its width or diameter. The elongatedmember has a plurality of radioactive seeds dispersed therein in apredetermined array.

In another embodiment, the substantially axially stiff andlongitudinally flexible elongated member comprises a single continuousmonofilament element of bio-compatible material that has a plurality ofseed sources molded therein. The bio-compatible material can bepreferably a bio-absorbable polymer or copolymer material thatencapsulates the plurality of radioactive seeds.

A further embodiment of the invention is characterized as asubstantially constant diameter solid elongated matrix member of abio-absorbable polymer with seeds positioned therein at predeterminedspacing along its length, whose diameter is a close fit to the needlelumen, thus preventing collapse as axial force is applied on theproximal end of the elongated matrix member. The space between the seedsources is maintained throughout the insertion and expulsion of theelongated matrix member. The diameter of the polymer between the seedsmay be slightly reduced in diameter in relation to the overall diameterof the elongated matrix member, but is of sufficient diameter so as tonot allow collapse of the matrix member within the needle lumen.

The present embodiment of the invention further allows for variation inany spacing between seeds, as the semi-rigid, deflecting elongate membercould be produced under a doctor's prescription for each patient, withoptimal seed distribution for a particular patients treatment program.

This one object of the invention is to provide an implant that can becustom made as specified by a prescription for an individual patient.

A related object is to provide a plurality of implants that can beeasily implanted at the same time.

Further aspects, objects, advantage and embodiment of the invention canbe understood from the specification, the figures and the claims.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is an enlarged side view of an embodiment of the therapeuticimplant of the invention.

FIG. 2 is an enlarged view of a cross section of an embodiment of thetherapeutic implant of the invention of FIG. 1.

FIG. 3 is an enlarged side view of the brachytherapy device includingthe implant of FIG. 1.

FIG. 4A shows a plurality of strand implants in accordance with theprior art.

FIG. 4B depicts a plurality of strand implants of an embodiment of theinvention with custom end spaces at the distal end of selected strandimplants.

FIG. 5A depicts needles containing strands of embodiments of theinvention aligned with a template.

FIG. 5B depicts the template of FIG. 5A with the custom strand implantspositioned in the tissue of the patient.

FIG. 5C depicts a top view of the embodiment of the invention asdepicted in FIG. 5B.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with an embodiment of the invention, a substantiallyaxially, semi-rigid and longitudinally flexible elongated member made ofmaterial, which is bio-absorbable in living tissue, is provided forinsertion in tumors. A plurality of radioactive seeds are encapsulatedand positioned in a predetermined array in the member in the desiredspaced relationships.

The seeds can be of various types having low energy and low half-lifesuch as Iodine seeds, known as I-125 seeds, consisting of a weldedtitanium capsule containing iodine 125 absorbed on a silver rod, orPalladium 103 seeds. Examples of radioactive seeds used to manufacturethe therapeutic element appear in Table 1 below.

TABLE 1 Seed Manufacturers and Common Types of Seeds. PART NUMBERMANUFACTURER SEED NAME IODINE ¹²⁵ 80040-A Amersham 6702 OncoSeed 80040-BAmersham 6711 RAPID Strand 80040-C North American Scientific IoGold80040-D Best Industries BEST Iodine-125 80040-E Bebig Symmetra 80040-FMills Biopharmaceuticals ProstaSeed 80040-G Syncor PharmaSeed 80040-HInternational Isotopes IsoStar 80040-I Implant Sciences I-Plant 80040-JInternational Brachytherapy InterSource-125 80040-K Source Tech STM125180040-L DRAXIMAGE, Inc. BrachySeed PALLADIUM ¹⁰³ 80035-A North AmericanScientific Pd Gold 80035-B Theragenics Theraseed 200 80035-C BestIndustries BEST Palladium-103 80035-D International BrachytherapyInterSource 103

Additionally, seeds can be manufactured using iridium 192, cesium 131,gold 198, yttrium 90 and phosphorus 32. Further radioactive isotopesused to manufacture seeds are not limited to these examples, but caninclude other sources of different types of radiation. In addition, itis to be understood that other types of seeds can be used. Inparticular, seeds such as those described in U.S. Pat. No. 6,248,057,which patent is incorporated herein by reference and which is entitled“Absorbable Brachytherapy and Chemotherapy Delivery Devices andMethods”, can be used with the present invention. These seeds includeradiation delivery devices, drug delivery devices, and combinations ofradiation and drug delivery devices in the form of beads, seeds,particles, rods, gels, and the like. These particular seeds areabsorbable wherein the radiation element or drug delivery element iscontained within, for example, absorbable polymers such as those listedbelow or in the above-referenced patent. In such seeds, thebio-absorbable structure can have a predefined persistence, which is thesame as or substantially longer than a half-life of the radioactiveelement contained in the bio-absorbable structure. These abovebio-absorbable seeds can be used in the same manner as the seedsdescribed herein with respect to the invention.

The substantially axially, semi-rigid, and longitudinally flexibleelongated member may be made of any of the natural and/or syntheticbio-compatible and bio-absorbable materials. Natural and syntheticpolymers and copolymers can be used. Examples of syntheticbio-absorbable polymer materials are the polymers and copolymers ofglycolide and lactide, polydioxanone and the like. Such polymericmaterials are more fully described in U.S. Pat. Nos. 3,565,869;3,636,956; 4,052,988 and European Patent Application No. 30822, all ofwhich are incorporated herein by reference. Specific examples ofbio-absorbable polymeric materials that can be used to produce thesubstantially axially stiff and longitudinally flexible elongated memberof an embodiment of the present invention are polymers made by ETHICON,Inc., Somerville, N.J., under the trademarks “MONOCRYL” and “MAXON,”which material is incorporated herein by reference.

Table 2 below provides examples of polymers (and manufacturers) suitablefor use in producing embodiments the therapeutic member of theinvention. A further discussion of such biodegradable polymers can befound in an article by John C. Middleton and Arthur J. Tipton entitled“Synthetic Biodegradable Polymers as Medical Devices”, published March1998 in Medical Plastics and Bio-materials, which article isincorporated herein by reference.

TABLE 2 Biodegradable polymers, properties and degradation time. DEGRA-MELTING GLASS- DATION POINT TRANSITION MODULUS TIME POLYMER (° C.) TEMP(° C.) (Gpa)^(a) (MONTHS)^(b) PGA 225-230 35-40 7.0 6 to 12 LPLA 173-17860-65 2.7 >24 DLPLA Amorphous 55-60 1.9 12 to 16 PCL 58-63 (−65)-(−60)0.4 >24 PDO N/A (−10)-0     1.5  6 to 12 PGA-TMC N/A N/A 2.4  6 to 1285/15 Amorphous 50-55 2.0 5 to 6 DLPLG 75/25 Amorphous 50-55 2.0 4 to 5DLPLG 65/35 Amorphous 45-50 2.0 3 to 4 DLPLG 50/50 Amorphous 45-50 2.0 1to 2 DLPLG ^(a)Tensile or flexural modulus. ^(b)Time to complete massloss. Rate also depends on part geometry.

The final hardness of the polymer of elongate member should preferablybe in a range from 20 to 80 durometers, and, more preferably, in therange of 20-40 durometers. The bio-absorbable material should preferablybe absorbed in living tissue in a period of time of from about 70 toabout 120 days, but can be manufactured to be absorbed anywhere in arange from 1 week to 1 year, depending on the therapeutic plan for eachspecific patient. Preferably, the bio-absorbable material is selected toabsorb about when the half-life of the radioactive seeds is reached.

The member or strand is fashioned with a manufacturing method known asinsert or compression molding. The radioactive seeds are placed into afixture that spaces the seeds at the appropriate intervals in a cavitythat is shaped to the desired final dimensions of the elongated member.All the spacings can be of different lengths, if the preoperativetherapeutic plan so specifies. The synthetic polymer is introduced intothe mold at a temperature that is above the melt point of the polymer.The polymer flows around the seeds within the cavity, surrounds theseeds and fills in the spaces between the seeds. After the mold hascooled, it is disassembled, and the finished elongated member isremoved. Because the polymer flows at temperatures significantly greaterthan 250° F., the therapeutic element can easily be steam sterilizedbefore implantation.

As specified above, the elongated member encapsulating radioactive seedsmay be fashioned using compression molding techniques. Compressionmolding forms the molded piece in a two part mold where the polymermaterial is placed within the cavities of the mold in a liquid state.The seeds are placed in position within the cavities filled with thepolymer and the mold is closed and compressed, then cooled to form apiece that conforms to the shape of the closed cavity.

The manufacturing process also can make the member echogenic. In thecase of the molding of the elongated member, air can be entrapped in thepolymer material. During the cooling stage of the molding process, themold is placed in a vacuum chamber and the air in the chamber isevacuated. This causes the entrapped air in the mold to come out ofsolution from the polymer, and as the mold cools, this air is entrappedwithin the cooling polymer in the form of minute bubbles suspended inthe plastic.

Air is a strong reflector of ultrasound energy, since the inherentimpedance of air is many times greater than body tissue. When theelongated member is introduced into the body and imaged with ultrasound,the elongated member is clearly visible in the resulting image, and is,thus, echogenic.

The resulting elongated member is now a single solid monofilament of thepolymer with the seeds spaced within the monofilament and encapsulatedat the appropriate intervals. The member is generally very axiallyflexible such that it can be bent back upon itself in a circle withoutkinking. However, the member has sufficient column strength along itslongitudinal axis so that the member can be urged out of a hollow needlewithout the member folding upon itself. Again, the intervals can beselected to be any distance or combination of distances that are optimalfor the treatment plan of the patient.

In FIG. 1, the therapeutic elongated element, member or matrix or strand10 is displayed having the semi-rigid, radially flexible polymer 12 andthe radioactive seeds 14. As can be seen in FIG. 1, the polymer fillsthe spacing segments 16 in a contiguous manner to fashion the totalelongate member.

FIG. 3 shows a side view of the brachytherapy device 20. The needle 22is shown partially broken away and has a sheath component 24, and isloaded with the therapeutic element or member 10. The beveled end 26 ofthe needle 22 is plugged with a bio-compatible substance 28. The plugprevents fluids and tissue from entering the needle and coming incontact with the member 10 prior to the placement of the member orstrand 10 adjacent the tumor. The plug 28 can be made out of a bone waxor can be made of one of the bio-absorbable polymers or copolymerslisted herein. Further, the plug can be the end of the member or strand10 that is heated and reflowed after the strand or member is insertedinto the needle. A stylet or stylus 30 is inserted into the needle untilit meets the therapeutic element or member 10. Then, the needle 22 isinserted into the site and the therapeutic member 10 is graduallyextruded from the needle via the static force of the stationary stylus30, as the needle 22 is pulled back.

Based on the above, it is evident that the present invention providesfor an embodiment having an elongated member, which is comprised of abiodegradable polymer, which encapsulates a plurality of spacedradioactive therapeutic seeds. The seeds can be spaced in custom mannerso that each member or strand is designed for the particular patient.That is to say that the spacing between each seed pair in a strand ormember can be different for each seed pair. Further, each individualstrand can have an entirely different seed spacing pattern than the nextstrand or member. Characteristically, or typically, for a surgicalprocedure, up to twenty-five of such strands or members are used toencircle the organ or tumor that is affected.

Further, such an arrangement provides for a strand or member that isstiff along its longitudinal axis. That is to say that the strand ormember has column strength or stiffness while the strand or member isflexible in the direction which is radial or substantially perpendicularto the longitudinal axis. Accordingly, the strand or member in apreferred embodiment is able to bend back upon and touch itself, whenformed in a characteristic length.

In other embodiments, the strand or member can be made with theincorporation of drugs and/or hormones and/or other therapeutics, whichare embedded in or formed in the polymer and/or seeds. Thus, theembodiment of the invention can deliver not only radioactive seeds, butsuch therapeutic drugs, hormones and other therapeutic devices. Inaddition, the strand or member can deliver heated seeds such as providedby ATI Medical of San Diego, Calif. These seeds can be preferably heatedto from about six (6) degrees centigrade to about seventy (70) degreescentigrade after being inserted into a patient in a preferredembodiment. ATI Medical is located at (www.ATImedical.com), andreference to such heated seeds is incorporated herein by reference.

It should be understood that other seed types can be used with thepresent invention. Thus, for example, in addition to the aboveencapsulated seeds, seeds which are made of radioactive or coiled wirescan be embedded in the polymer and be within the spirit and scope of theinvention. These seeds can be individual seeds, which are spaced withina polymer, or a continuous seed which extends the length of the strandor member.

Further to the invention, as discussed above, it should be understoodthat the strand or member can be made echogenic by the incorporation of,for example, air bubbles 32 in the polymer spaces between the seeds, ascan be seen in FIGS. 1 and 3. These air bubbles or pockets can be formedin the polymer in ways identified above and other ways known to one ofskill in the art.

According to the above, the advantages of the improved delivery systemsubmitted of the present invention are:

1. The substantially axially stiff and longitudinally flexible elongatedmember allows controlled placement of the plurality of radioactive seedsthat are encapsulated and positioned in a predetermined array in themember without migration of the individual radioactive seeds during thetime the seeds are treating the tumor.

2. The fixed linear positioning of the seeds minimizes “hot” and “cold”radiation spots due to undesirable movement of the seeds.

3. The normal tissue is spaced away from the seed surface by thethickness of the body of polymer, to decrease necrosis from a high localdose.

4. The axial stiffness of the elongated member allows the elongatedmember to be urged out of the needle as the needle is withdrawn, withoutthe member jamming in the needle, by collapsing or expanding as theneedle is withdrawn from the tumor site.

5. The longitudinal flexibility of the elongated member allowslocational accuracy to be maintained as the gland shrinks topre-procedural size, as the swelling that occurs during tissuedisruption and needle manipulation recedes.

6. Increased speed of implant resulting in reduced surgical time andhealth care provider radiation exposure.

Method of Delivering Customized Strands and/or Members Per a TherapeuticPrescription:

As is known in the industry, there is software which can be used toprovide brachytherapy treatment planning guides which are customized foreach individual patient. Such software is provided by Rossmed, which islocated at Ross Medical, 7100, Columbia Gateway Drive, Suite 160,Columbia, Md. 21046. This particular software, which is incorporatedherein by reference, is known as the Strata suite, which software helpsphysicians to develop and visualize low dose rate brachytherapytreatment plans for treating malignant tumors in human tissue. Thetreatments entail the use of radioactive seed sources, which areimplanted adjacent to the malignant tissue. The Strata software usesimaging to create a three-dimensional reconstruction of the patient'sanatomy. The software is able to plan the placement of the seeds withinthe target. The radiation dose that is delivered to the target can becomputerized and visualized using the software. The software can thenspecify an optimal number of strands or members along with optimal seeddosages and spaces between seeds. At times, the loading plans sospecified cannot be optimized by the physician in preparing the seed andspacer loads for the needles, as the spacers come in only predefinedlengths.

Accordingly, with the present invention, the software can be used toprepare a prescription, which optimizes the number of members orstrands, and placement and spacing of seeds for each of the strands ormembers. This optimization plan can then be sent to a manufacturingsite. By using the techniques of an embodiment of the present invention,an optimized strand or member can be created with the specified numberof seeds and the specified distances between each seed pair. Once thisprescription is filled at the manufacturing site, the custom strand ormember can be sent back to the physician for treatment of the patient.With such an arrangement, radiation patterns can be optimallyestablished for the treatment of each patient. Further, the preparationtime for the physician is greatly diminished as the physician does nothave to hand assemble and hand load the seeds and spacers into theneedle.

By using the diagnosis software to obtain precise dimensions of thetarget tumor or tissue, each individual strand can becustom-manufactured in such a way that the placement of seeds coincideswith the target tissue precisely, while maintaining the same depth ofimplantation for a plurality of strands. All a physician has to do is toimplant each strand in its designated spot to the same depth (forexample, all strands would be implanted flush again a tissue surface),and the seeds will be placed correctly within the treatment tissue. (Inother words, no seeds will protrude beyond the boundaries of thetreatment tissue.)

Improved Implantation Method and Seed Strands

As is known to the practitioner, generally prior art seed strands comein a fixed length. To correctly place each seed at its designated spot,previous methods required injecting hollow needles into the tissue andthen retracting each needle by a certain amount before the strands canbe implanted at the correct depth. FIG. 4A shows an exemplarypre-operative diagnostic plan created by the methods and softwarediscussed above. Each strand 401, 402, 403 and so on can have adifferent number of seeds and spacing between the seeds, and each strandtypically have a seed proximate to the distal, or pointed, end. Needlesnumbered 1 through 21 in this example are urged fully into a fixed depthdesignated as 0.00 cm, and then retracted as needed. Needle #1, forexample, is retracted 1.00 cm before the seed strand is implanted intothe tissue. For needle #2, the needle need not be retracted beforeimplantation because a seed is to be deposited at the 0.00 cm depth. ForNeedle #5, the retraction distance is 1.50 cm, and so on. We can seeeach needle can have a different retraction amount, making theimplantation operation cumbersome and time-consuming. It is quitenaturally desirable to provide a method and seed strand that canovercome this disadvantageous process.

Refer to FIG. 4B, the present embodiments of the invention provide forcustom seed strands and a method to significantly shorten theimplantation time. The strands are of substantially uniform length, butwith distal ends 41 of individual strands having customized end spacersso that the physician can implant each strand to the same depth. In thediagrams, the distal ends are shaded only for clarity. In a preferredembodiment of the invention, the distal ends could be made of the samepolymeric material as the strand body. The spacings between the seeds,and the custom distal end spacing are provided in the strand inaccordance with the methods presented above.

With the use of these novel implants, the physician need not beconcerned about the depth of the implant as each needle is urged intothe patient to the same depth and each strand would be implanted at thatdepth as the needle is pulled back leaving the strand in place. There isno need to identify the distal end of each strand by ultrasound orvisual inspection, or to specially position each strand to a customdepth. There is no concern or need to retract a needle before implantingany strand. Accordingly, the elapse time for the surgical procedure isshortened with less exposure of the physician to the strand and lesstime that the patient must endure the procedure.

According to the invention, the strands are implanted into the patientaccording to a location map and an implantation plan. Each strand isimplanted to the same depth. The implantation map can be marked onto thepatent or can be applied to a pliable material that is laid over theimplant site. Implantation can also occur without such a map and inaccordance to an implantation plan.

Another embodiment of the invention uses an exemplary device or template53 as discussed below and as depicted in FIG. 5A. FIG. 5A shows anembodiment of the invention, which allows for multiple implantations ofstrands at once. A plurality of treatment strands according to theinvention 51 (as loaded into implantation needles 52, not shown) can bealigned and held in place by an exemplary device 53 that has a pluralityof receptacles 54 for the needles to pass through. Each custom-madestrand, with custom-spaced seeds 51 a and custom distal ends 51 b(shaded in the diagram), is loaded into its individually designatedreceptacle. Note that it may not be necessary to load all receptacleswith a strand (see unloaded receptacle 44 a) if the tumor to be treatedis small in size.

Next, the template, having a substantially flat surface 53 a on thebottom side, is maneuvered and positioned onto a tissue surface 55 ofthe patient FIG. 5B. Said tissue surface 55 may be an outer epidermis ofthe patient if the procedure is non-surgical, or an inner dermis if theprocedure is surgical. After the device is positioned, all the loadedstrands can be implanted at the same time to the same depth 56. As eachneedle is removed, the strand is left in place. As each strand has acustom spacer end there is no need for the physicians to withdraw anyneedle a specific amount as taught by the prior art, prior to the strandbeing dispensed from the needle. Accordingly, time is conserved duringthe implantation procedure. Once the strands are implanted, all theseeds will be properly aligned according to the pre-operative treatmentplan. The template is then removed.

By using the template as a guide and the customized strands, thetreating physician does not have to be concerned about variations in theimplantation depth of each implant. Further, if multiple needles areinjected at once, this method can substantially reduce the time neededfor the procedure.

Subsequent rows of implants can be implanted by repeating the procedureoutlined above. See FIG. 5C, which depicts a top view of the same tumordepicted in FIG. 5B, showing rows 58 of implants implanted by theprocedure. In another embodiment, the template may have multiple rows,allowing for an even greater number of implants at once.

Additional aspects, objects and advantages of the invention can beobtained through a review of the appendant claims and figures. It is tobe understood that other embodiments can be fabricated and come withinthe spirit and scope of the claims and the invention.

The foregoing description of preferred embodiments of the presentinvention has been provided for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Many modifications andvariations will be apparent to one of ordinary skill in the relevantarts. It is intended that the scope of the invention be defined by theclaims and their equivalence.

1. A therapeutic kit, comprising: a plurality of treatment strandsconfigured to be implanted into a patient to a same depth; wherein eachsaid strand includes a distal end and a proximal end; wherein each saidstrand includes one or more treatment seeds located between the distaland proximal ends of the strand; wherein each of at least two saidstrands includes a custom distal end spacer provided between the distalend of the strand and the treatment seed located closest to the distalend of the strand; wherein the custom distal end spacers in the at leasttwo said strands cause the treatment seeds located closest to the distalends of the strands to be spaced relative to the distal ends of thestrands, according to a treatment plan, when the distal ends of thestrands are implanted to the same depth using needles inserted to thesame depth; and wherein the custom distal end spacer of one said strandhas a different length than the custom distal end spacer of a secondsaid strand.
 2. The therapeutic kit of claim 1, wherein the plurality ofstrands have a same length.
 3. The therapeutic kit of claim 1, furthercomprising a needle for each said strand, wherein each said needle isloaded with one said strand.
 4. The therapeutic kit of claim 3, furthercomprising a stylet for each said needle.
 5. The therapeutic kit ofclaim 1, wherein the treatment seeds comprise radioactive seeds.
 6. Thetherapeutic kit of claim 1, wherein the treatment seeds comprise heatedseeds.
 7. The therapeutic kit of claim 1, wherein for each strand thatincludes more than one seed, pairs of seeds in the strand are spacedapart from one another according to the treatment plan.
 8. Thetherapeutic kit of claim 1, wherein each said strand includes abio-absorbable material that encapsulates the one or more seeds of thestrand.
 9. The therapeutic kit of claim 1, wherein the custom distal endspacers comprise a bio-absorbable material.
 10. A therapeutic kit,comprising: a plurality of treatment strands configured to be implantedinto a patient; wherein each said strand includes a distal end and aproximal end; wherein each said strand includes one or more radioactivesources located between the distal and proximal ends of the strand;wherein each of at least two said strands includes a custom distal endspacer provided between the distal end of the strand and the radioactivesource located closest to the distal end of the strand; wherein thecustom distal end spacers in the at least two said strands cause theradioactive sources located closest to the distal ends of the strands tobe spaced relative to the distal ends of the strands, according to atreatment plan, when the distal ends of the strands are implanted to thesame depth; and wherein the custom distal end spacer of one said strandhas a different length than the custom distal end spacer of a secondsaid strand.
 11. The therapeutic kit of claim 10, wherein each of theradioactive sources is selected from a group comprising: a radioactiveseed; a radioactive coil; and a radioactive rod.
 12. A method,comprising: accepting a tissue treatment plan for the tissue to betreated, which treatment plan specifies a number and spacing oftreatment seeds to be provided in the treatment plan; and creating aplurality of treatment strands, at least two of which includes a customdistal end spacer provided between the distal end of the strand and thetreatment seed located closest to the distal end of the strand; whereinthe custom distal end spacers cause the treatment seeds located closestto the distal ends of the strands to be spaced relative to the distalend of the strands, according to the treatment plan, when the distalends of the plurality of strands are implanted to a same depth; andwherein at least two of the custom distal end spacers differ in length.13. The method of claim 12, wherein the creating step comprises creatingthe plurality of strands so that they have a same length.
 14. The methodof claim 12, further comprising loading each of the strands into aseparate needle.
 15. A method for treating a patient with a plurality oftreatment strands, wherein each of at least two of the treatment strandshas a custom distal end spacer between a distal end of the strand andthe treatment seed located closest to the distal end of the strand, themethod comprising: inserting a first needle to a first depth to therebyimplant a first one of the strands to the first depth; and inserting aplurality of further needles to the first depth, to thereby implantfurther strands, of the plurality of strands, to the first depth;wherein the custom end spacers of at least two of the plurality oftreatment strands have different lengths, thereby causing the seedslocated closest to the distal ends of the at least two strands to beimplanted to different depths.
 16. The method of claim 15, wherein thefirst and further needles are inserted through different receptacles ina template.
 17. A method for treating a patient with a plurality oftreatment strands, wherein each of at least two of the treatment strandshas a custom distal end spacer between a distal end of the strand andthe treatment seed located closest to the distal end of the strand, themethod comprising: inserting a plurality of needles to a same depth,wherein each needle is loaded with one of the plurality of strands; andimplanting the plurality of strands to the same depth; wherein thecustom end spacers of at least two of the plurality of treatment strandshave different lengths, thereby causing the seeds located closest to thedistal ends of the at least two strands to be implanted to differentdepths.
 18. The method of claim 17, wherein the first and furtherneedles are inserted through different receptacles in a template.
 19. Amethod, comprising: accepting a tissue treatment plan for the tissue tobe treated; and creating the plurality of treatment strands, such thatat least two of the strands includes a custom distal end spaceraccording to the treatment plan; wherein the custom distal end spacerscause the treatment seeds located closest to distal ends of thetreatment strands to be spaced relative to the distal ends of thetreatment strands according to the treatment plan; wherein the customdistal end spacers allow a health care professional to implant thestrands to a uniform depth in the tissue to be treated; and wherein atleast two of the custom distal end spacers have different lengths. 20.The method of claim 19, wherein the creating step includes positioningtreatment seeds in the strands according to the tissue treatment plan.